1. Field of the Invention
The present invention relates to fuel delivery systems that are adapted to deliver fuel from a fuel tank to an engine, e.g., an internal combustion engine for an automobile.
2. Description of the Related Art
Various fuel delivery systems are known and include a first known fuel delivery system that will be hereinafter described. As shown in FIG. 5, the first known fuel delivery system includes a substantially cup-shaped reservoir 110, a set plate 111, a fuel pump 113, a fuel filter 120, a pressure regulator 122, and a jet pump 124. The reservoir 110 is placed on a bottom plate 102 of a fuel tank 101. The set plate 111 has a fuel discharge pipe 112 communicating between the inside (interior) and outside (exterior) of the fuel tank 101. The set plate 111 is placed to close an opening 104 formed in a top plate 103 of the fuel tank 101. On the outside of the fuel tank 101, the fuel discharge pipe 112 is connected to an engine via a fuel delivery pipe 106.
The fuel pump 113 is an electrically driven fuel pump and is disposed within the reservoir 110. A suction-side filter 115 is fitted into a suction port (not shown) of the fuel pump 113. A check valve 117 is disposed within a discharge port 113a of the fuel pump 113 in order to maintain residual pressure in the fuel system. The fuel pump 113 has a relief port 113b into which a relief valve 119 is assembled to form a relief valve device.
A fuel filter 120 is disposed so as to surround the circumference of the fuel pump 113 and has a substantially annular configuration. A first pipe Ka connects the discharge port 113a of the fuel pump 113 and a fuel inlet port (not shown) of the fuel filter 120 to one another. A second pipe Kb connects the fuel outlet port (not shown) of the fuel filter 120 and the fuel discharge pipe 112 of the set plate 111 to one another.
The pressure regulator 122 is disposed on the fuel filter 120 and has a return port 122a through which the surplus fuel within the fuel filter 120 is discharged. The jet pump 124 is disposed at the bottom of the reservoir 110. A third pipe Kc connects the return port 122a of the pressure regulator 122 and an introduction port 124a of the jet pump 124 to one another.
According to the first known fuel delivery system, as the fuel pump 113 is driven, the fuel within the reservoir 110 is pumped through the suction-side filter 115 and is then supplied into the fuel filter 120 via the discharge port 113a and the first pipe Ka. Thereafter, the fuel passes through the fuel filter 120 and is further supplied into the engine via the second pipe Kb, the fuel discharge pipe 112 of the set plate 111, and the fuel delivery pipe 106. On the other hand, the surplus fuel within the fuel filter 120 is supplied into the introduction port 124a of the jet pump 124, via the return port 122a of the pressure regulator 122 and the third pipe Kc. At the jet pump 124, the fuel within the fuel tank 101 is transferred into the reservoir 110 due to the flow of the return fuel that is discharged from the return port 122a of the pressure regulator 122. Arrows indicate the path of the flow of the fuel in FIG. 5.
When the fuel pump 113 is stopped, the check valve 117 is closed so that a residual pressure of fuel can be maintained within the passageway of the fuel communicating with the engine.
Japanese Laid-Open Patent Publication Nos. 63-85254 and 2001-20900 teach fuel delivery systems in which jet pumps are operated by fuel discharged from pressure regulators as described in the first known fuel delivery system.
In addition to the first know fuel delivery system, the known fuel delivery systems also include a second known fuel delivery system that will be hereinafter described. The second known fuel delivery system is similar to the first known fuel delivery system and will only be described with respect to the elements that are different from those of the first known fuel delivery system
As shown in FIG. 6, according to the second known fuel delivery system, one end of the third pipe Kc is connected to the return port 122a of the pressure regulator 122, while the other end of the third pipe Kc opens into the reservoir 110 in a position adjacent to the bottom of the reservoir 110. In addition, a three-way pipe 200 is disposed so as to intersect the second tube Kb. A branch port 201 of the three-way pipe 200 is connected to the introduction port 124a of the jet pump 124 via a fourth pipe Kd. Further, a check valve 217 is assembled within the fuel discharge pipe 112 of the set plate 111 in order to maintain the residual pressure.
According to the second known fuel delivery system, the surplus fuel within the fuel filter 120 returns to the reservoir 110 via the return port 122a of the pressure regulator 122 and the third pipe Kc.
On the other hand, a part of the fuel that flows through the second pipe Kb is supplied into the introduction port 124a of the jet pump 124 via the three-way pipe 200 and the fourth pipe Kd. Further, at the jet pump 124, the fuel within the fuel tank 101 is transferred into the reservoir 110 due to the flow of the fuel that is discharged from the fourth pipe Kd. Furthermore, when the fuel pump 113 is stopped, the residual pressure of the fuel within the fuel passageway communicating with the engine may be maintained because the check valve 217 within the fuel discharge pipe 112 is closed.
Japanese Laid-Open Patent Publication No. 2002-250255 teaches a fuel delivery system in which a jet pump is operated by the flow of the fuel that is diverged from the flow of the fuel supplied to the engine, as in the second known fuel delivery system.
In case of the first known fuel delivery system shown in FIG. 5, the returned fuel from the pressure regulator operates the jet pump 124. Because the backpressure of the jet pump 124 increases as the diameter of a nozzle 124b of the jet pump 124 decreases, there exists a limitation in minimizing the diameter of the nozzle. Although a relief valve may be assembled within the jet pump 124, there still exists a limitation in minimizing the diameter of the nozzle. Thus, when the backpressure exceeds a predetermined value, the flow of the fuel supplied to the jet pump 124 may be reduced due to an inability to open the pressure regulator 122.
In the case of the second known fuel delivery system shown in FIG. 6, the pressure regulator 122 may adjust the pressure of the fuel even if the backpressure has been increased due to a diameter reduction of the jet pump 124 nozzle. Therefore, the diameter of the nozzle of the jet pump 124 may be reduced without causing the problems of the first known fuel delivery system shown in FIG. 5. In addition, the performance of the jet pump 124 can be improved because no additional relief valve is required for releasing pressure when the backpressure ahead of the jet pump 124 exceeds a predetermined value.
However, the second known fuel delivery system requires the three-way pipe 200 for diverging a flow of fuel away from the flow of the fuel supplied to the engine. In addition, the check valve 217 is required for maintaining the residual pressure on the upstream side of pipe 106, or in other words, within the fuel flow path communicating with the engine. These additional components may cause an increase in manufacturing costs for the second known fuel delivery system. Therefore, the improved performance of the jet pump is obtained only though an associated increase in manufacturing cost.